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retract servo suggestion needed

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Old 02-06-2002, 05:15 PM
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chris-s
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Default retract servo suggestion needed

Hi folks,

I need a servo to actuate two mechanical retracts. Last time I did this, a standard (futaba s148) wasn't quite strong enough so a bought a hi-tec retract servo only to find out that it would only move thru 180 degrees, in that case I did a 'genetic' modification by connecting the mechanism to the s148 electrics and got it proportional, however, I don't really want to do that again.

So what can you suggest that is not a fixed 180 degree movement and cheap'ish? Size wise it should be as per a standard S148.

Cheers,

Chris
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Old 02-06-2002, 05:31 PM
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Ron S
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Default retract servo suggestion needed

Well, the thing you need for a retract servo, is a lot of throw, and a lot of torque. By using a standard servo, you give up on both. If you swap out the standard servo, and go to a higher torque servo, you gain on the the torque only. The throw is still +/- 45 degrees or so. You do gain ATV adjustment capability, but the you lose on throw!

You could use 2 standard cheapo servos - each servo placed near the retract mechanism, to eliminate slop, and use a y-harness...

The right thing to do though, IMO, is to use the retract servo properly. I have a pattern plane that is probably 7 years old or so, and the Futaba S-136G (?) retract servo still works fine, for operaqting the mains, and the nose gear. The servo, along with the HiTec you spoke of, was designed for hi torque, capable of max throw per servo arm length (180 degrees - can't get any more than that...), and you even get a more realistic retract speed due to the gearing.

You could use air cylinders, but why make it more difficult if a single retract servo should work?

Good luck...
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